This paper describes a study of the hydration of belite-yeelimite ferrite (BYF) cements, made from clinkers comprising principally belite (C2S), with yeelimite (C4A3$) and ferrite (C4AF) as the two main secondary phases, and inter-ground with calcium sulfates.The clinkers used in this study also contained some boron in order to stabilize alpha-C2S at room temperature.The main hydration products of these cements at early ages are the same as the products of yeelimite hydration in presence of calcium sulfate: ettringite, calcium monosulfoaluminate, and aluminum hydroxide.At later ages, this initial product assemblage is modified by the hydration of the belite and ferrite phases, producing straetlingite, siliceous hydrogarnet and C-S-H, while aluminum hydroxide is consumed.The changes in the phase assemblage during hydration were calculated by thermodynamic modeling based on the cement database CEMDATA07 updated with recent data on siliceous hydrogarnets.Thermodynamic calculations were carried out using the GEMS approach for BYF cements with high and low yeelimite content and compared to the experimental data obtained by XRD and TGA.The equilibrium predictions matched well with the experimental results at longer reaction times.However, at early reaction times the phase assemblage obtained is strongly influenced by kinetics.